A symmetrical power semiconductor device must be capable of withstanding substantially the same voltage in both directions. In order to be able to withstand a voltage of about 1,000 volts, for example, it is particularly necessary to take effective peripheral dispositions, and for them to be as simple as possible to fabricate.
It is also advantageous to be able to take these dispositions on one face only of the semiconductor. In this context, a prior method consists in bringing the periphery of a bottom junction in a power semiconductor up to its top face by forming pairs of touching slabs which are diffused from both of the main faces of the semiconductor.
For high voltage devices, the slabs may reach a depth of at least 200 .mu.m, and this requires a very long diffusion time. The provision of the slabs can be accelerated by thermomigration of aluminum, but such a method is difficult to implement without disturbing the other characteristics of the device.
The object of the invention is to bring out, on a first face of a symmetrical power semiconductor device, the periphery of a junction situated close to a second face of the device, while avoiding the difficulties inherent to diffusing deep peripheral slabs.
The invention also seeks to make such a device benefit from the facilities offered by epitaxial technology.